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Model GFC7000E Instruction Manual TROUBLESHOOTING & REPAIR PROCEDURES
04584 Rev A1 196
4. Confirm the sample pressure, wheel temperature, bench temperature, and sample flow
readings are correct and have steady readings.
5. Disconnect the exhaust line from the optical bench near the rear of the instrument and plug
this line into the SAMPLE inlet creating a pneumatic loop. The CO
2
concentration (either zero
or span) now must be constant. If readings become quiet, the problem is in the external
pneumatics supplies for sample gas, span gas or zero air.
6. If pressurized span gas is being used with a zero/span valve option, make sure that the
venting is adequate (See Section 3.1.2 and 5.4)
7. If it is the zero point that is non-repeatable, and if that non-repeatability seems to only occur
at a certain time of day, such as when worker occupancy is highest or lowest, make sure the
flow of purge gas to the GFC wheel housing has not stopped (see Sections 10.2.2 and 11.1.7.
for more information).
11.2.3. Inability to Span – No SPAN Key
1. Confirm that the carbon dioxide span gas source is accurate; this can be done by switching
between two span-gas tanks. If the CO
2
concentration is different, there is a problem with
one of the tanks.
2. Check for leaks in the pneumatic systems as described in Section 9.3.3.
3. Make sure that the expected span gas concentration entered into the instrument during
calibration is the correct span gas concentration and not too different from expected span
value. This can be viewed via the RNG Menu (see Section 6.7).
4. Check to make sure that there is no ambient air or zero air leaking into span gas line.
11.2.4. Inability to Zero – No ZERO Key
1. Confirm that there is a good source of zero air. Dilute a tank of span gas with the same
amount of zero air from two different sources. If the CO
2
Concentration of the two
measurements is different, there is a problem with one of the sources of zero air.
2. Check for leaks in the pneumatic systems as described in Section 9.3.3.
3. The Internal zero air scrubber may need maintenance. This device is only present if the
analyzer has had zero/span valve options 51 or 53 installed this.
4. Check to make sure that there is no ambient air leaking into zero air line.
11.3. Other Performance Problems
Dynamic problems (i.e. problems which only manifest themselves when the analyzer is monitoring
sample gas) can be the most difficult and time consuming to isolate and resolve. The following
section provides an itemized list of the most common dynamic problems with recommended
troubleshooting checks and corrective actions.